In wellbore completions, it can be advantageous to dispose a gravel (or sand) pack in an annulus between a sand screen and the wellbore. Such gravel packs can act as a filter, preventing solids from the formation from proceeding through the sand screen and reaching the interior of the completion, e.g., to production tubing, etc.
Gravel packing generally includes setting a packer and depositing a gravel packing material (e.g., gravel and/or sand) in an annulus defined below the packer and between the wellbore and the gravel packing service tool. Prior to such operation, the service tool may be deployed into the wellbore and, subsequent to and/or during gravel packing, the service tool may be partially withdrawn from the wellbore. However, as this tool is deployed or retracted through the packer, it occupies an increasing or decreasing volume, respectively, in the wellbore below the packer. If the annulus above the packer remains sealed off from the wellbore below, such withdrawal and advancement of the service tool can have a piston-like effect on the wellbore below the packer, known as “swabbing.” Such increasing and decreasing displacement and/or pressures on the fluid can damage the gravel pack.
To avoid this, the inner bore of the service tool is provided with a valve at its distal end, sometimes referred to as a “full bore valve.” The valve is generally opened as the tool is advanced or removed, allowing pressure to communicate between the lower part of the wellbore and the portions of the wellbore above the packer. While such valves are acceptable for a wide variety of uses, during certain operations (e.g., reverse circulation to clean the wellbore annulus above the packer) the valve is closed while the service tool is moved, which can result in the undesired swabbing effect.